Definition of "tart"

Sharp to the taste; acid; sour.  examples

(of wine) high or too high in acidity.  examples

(figuratively) Sharp; keen; severe.  examples

A type of small open pie, or piece of pastry, now typically containing jelly (US) / jam (UK) or conserve, or sometimes other fillings (chocolate, custard, egg, butter, historically even meat or other savory fillings).  examples

A melt (block of wax for use in a tart burner).  examples

(Britain, slang) A prostitute.

(Britain, slang, derogatory, by extension) Any woman with loose sexual morals.  quotations

To practice prostitution.  examples

To practice promiscuous sex.  examples

To dress garishly, ostentatiously, whorishly, or sluttily.  examples